The wound repair mechanisms used to mend a tear in the membrane of a single cell and those that restore epithelial integrity to multicellular tissue wounds operate on massively different scales, but both are critical for survival and involve a series of ancient and highly conserved processes. Cell and tissue repair is thus of both fundamental cell biology interest and significant clinical relevance. The general aim of this proposal is to understand the biological basis of both cell and tissue wound repair within the in vivo context of a whole organism. We are particularly interested in the coordinated regulation of the actin/microtubule cytoskeletons and in the role of actin nucleation factors in these processes. This study proposes to investigate the mechanisms of wound repair in Drosophila in order to utilize its amenability for live imaging in concert with its superb genetic tractability not available in current wound healing models. We have recently developed a single cell wound healing model in Drosophila syncytial embryos that along with the multicellular tissue wound healing model of later staged embryos allows easy comparison of repair in wildtype versus embryos mutant for candidate wound genes, and that makes it possible to screen for novel genetic players in these repair processes. The specific aims of this proposal are to use combined molecular, genetic and cell biological approaches to: 1) examine the roles of the actin and microtubule cytoskeletons in single cell and multicellular tissue wound repair;2) characterize the functions of the Rho1 GTPase as a regulator of both wound repair processes;and 3) identify the components/machineries and regulatory pathways of both repair processes. Our long-term goal is to understand precisely the players and events that regulate these differently scaled wound repair processes. The morphological movements associated with wound repair share many similarities with normal morphogenetic events. Thus, the properties we learn here will impact our understanding of the basic biological events and regulations that underlie normal morphogenesis. Our studies will also be of fundamental clinical significance in many disease situations besides simply that of skin repair and is expected to provide insight that may guide further design of tissue repair therapies to enhance healing speed and/or prevent scarring, as well as for tissue engineering central to reconstructing tissues. PUBLIC HEALTH RELEVANCE: The capacity of an organism to repair a wound is a basic survival mechanism. The human body is subject to injuries to both multicellular tissues such as the skin, and to single cells such as muscle cells, and must be able to rapidly repair both types of damage to prevent infection and to restore function. The proposed studies use the fly embryo as a model organism in which to define the precise details of wound repair and compare that to normal developmental processes. Our findings can be easily extrapolated to vertebrate models, and will be useful in the design of new wound repair therapies that may speed the healing process and/or prevent excessive scarring.